"Europe represents material, political and symbolic benefits. It means prosperity, development and peace," he says.

Some analysts suggest debate on the charter has been limited in Spain because Spaniards do not think they have much to lose.

"Europe has always been good news in Spain, and that remains unchallenged," says Anna Verges, of the School of Law at Manchester University.

Mr Torreblanca agrees: "We do not open debates as to why the sun rises from the east."

Calling for a 'no'

Many Spaniards may not think they have much at stake in Sunday's vote - but a small minority made up of regional nationalists and a far-left party are calling for a "no".

Some regional nationalists in Catalonia and Galicia oppose the charter because they feel the constitution does not include a sufficiently regional dimension.

Left-wing opponents argue that the EU charter should do more. The United Left party says the constitution favours free market policies over social welfare and is too-pro American.

SPAIN AND THE EU

Since joining the EU in 1986:

EU subsidies of more than 100bn euros pumped into Spain's economy

European funds have financed 4km out of every 10km of Spanish highways

Helped to create 300,000 jobs a year

Protesters at a small but jubilant rally in Madrid agree, as drummers energise the eclectic group of activists.

For Juan Hargoindey, the charter is a missed opportunity to create a federal Europe.

"I am not a Euro-sceptic - I'm the opposite," he says.

"This is not a real advance," adds the spokesman for Another Democracy is Possible - the main group campaigning against the referendum, made up of civil society groups and green associations.

"Brussels is still a bureaucratic entity with little chance for citizens to influence it," Juan Carlos Madronal says.

All eyes on turnout

But observers say abstention, not opposition, is the Spanish government's real fear for Sunday.

Those campaigning for a No vote are in the minority

"The government wanted to make it significant" that Spain is set to launch the referendums, says Peru Egurbide, diplomatic correspondent for Spanish newspaper El Pais.

Spanish Prime Minister Jose Luis Rodriguez Zapatero is hoping that a resounding yes will give the constitution momentum across Europe, observers say. A very low turnout could mar his government's victory.

But while commentators speculate some right-wing Spaniards could use abstention from the poll to punish Mr Zapatero's government, they say there is less at stake in a low turnout for the Spanish government than for the charter itself.

"A low turnout would damage the credentials of the constitution - not Spain - in Europe," Mr Torreblanca says.

Pro-EU leaders across the continent will be hoping that Spaniards share Marta's enthusiasm for greater European integration.